Piston for engines



Patenten/lay 15, 1ers.`

UNITEl STTES PATENT erica.

ROLLAND s. Tao'r'r, or DENVER, comme.

PISTON FOR ENGINES,

Application led April 7, 1922. Serial No. 550,345.

T o all whom z't may concern.' l

Be it known that I, ROLLAND S. TRo'rT, a citizen of the United States, residing at Denver, county of Denver, and State of Colorado, have invented certain new and vuseful Improvements in Pistons for Engines, of which the following is a specification.

The object of my invention is to provide a flexible skirted piston which will be an4 improvement over the latest iston invented b f my friend and associate, r.` Charlie E.

atch, the serial number of his patent application being 538,906, and the date of filing February 24th, 1922.v A

A further object is to provide in a flexible skirted piston having all the practical advantages ofthe above named piston, a construction which will be better adapted to the die-casting process used in large production of aluminum alloy pistons.

` In the Hatch piston the wrist pin lugs depend from the head portion and are entirely separate from the skirt portion.

This produces a flexibility which, at least at some points, is much greater than is actually necessary, and which naturally reduces the strength of the piston.

In my piston', thewrist pin lugs on the side that takes the thrust of the connecting rod on the power stroke, are attached to the skirt to within a short distance of. the lower extremity of the lugs.

In the Hatch piston, the portion -of the l skirt directly below the center of the wrist pin is lthe weakest and hence the most ilexible part of the skirt, so that it seems to me that at this point lmost of the very .slight movement that occurs in any case, will take place.

If this is true, then connecting one side of the lug to theskirt, while greatly strengthening the piston, detractsbut little from its flexibility. .So that this construction should be practically as flexible and much stronger than the Hatch construction. And,'by providing more relief, over a wider area adjacent vthe extremities of the wrist pinbore, any danger of scoring at these points will be overcome. t

As `in the Hatchpiston, one side of the skirt is split by a single,'slightly diagonal,

' the wrist in lugs. n 1i longitudinal out2- connecting with a transverse cut which joins the apertures adjacent jfrom In the atch piston, a post, separate the walls of the head portion, connects the skirt on either side of the longitudinal cut with the piston head.

This has worked out beautifully in practice, but it is very diflicult to cast properly, especially by vthe die-casting process, where the metal cores must be removed from between these posts and thewall of the head portion of the piston. Y

We have .also noticed that when the steel expansion ring is in place in the Hatch piston, the longitudinal cut is tapered, being considerably wider at the lower extremity of the piston, which indicates that each post with its connected skirt part acts as a hinge swinging about the junction point of the post with the piston head. So, there is much less movement just below the transverse cut than there is at the lower extremity of the skirt. This is shown by the taper of the out as'stated above.

But, the movement'just below the transverse cut has proven to be lamplefor any condition, so the greater possible movement at the lower extremity of the skirt is much more than is necessary.

In other. Words, our experiments have shown us that though very little movement is required, a certain small amount is positively necessary over the entire surface of the skirt which touches the cylinder wall; that is, any rigid point touching the cylinder wall 'must have a flexible point directly opposite it.

In other words, if, asin my piston, less t Hence, I see no reason for providing any ,part 'of the skirt with the excessive and unnecessary flexibility of the lower extremity of the skirt of the Hatch piston.

That is, if the entire surface of the skirt has no more flexibility than that portion of the Hatch piston just belowA the transverse' cut, the results should be as good as if a greater, but 'un-used flexibility were prov vided;

For. the skirt does not have to expand even so muchas a sixteenth of an inch; a matter` of a few thousandths ig all that is required,

or possible; but that few thousandths mustl positively be provided over the entire 4skirt surface for more than 180o in extent.

. lthat I desire to provide, but I desire that much for the entire surface of the skirt for more than 180.

Hence, instead of connecting the skirt on either side of the longitudinal cut with the piston head by posts, I connect it to the rigidly supported wrist pin -lugs by ribs designed to provide the amount of flexibility desired. In other words, I use the wrist pin lugs and their supports to take the place of the posts in the Hatch piston. v r

In the drawings, Figure 1 is a side .elevation of my piston looking at right angles to the wrist pin bore; Figure 2 is aside elevation in partial section, taken at right angles to Figure 1; FigureB is an end elevation of thel plston showing a modified form of the ribs Vconnected to the wrist pin lugs and supzporting the skirt adjacent the longitudinal cut; :and Figure 4 is a'horizontal sectional view taken on the line of the wrist p1n bore and the line X-X of Figure 1.

The wrist pin lugs 1 are rigidly attached i to the head 1a by the external ribs 2, and the internal ribs 3, and areseparated from the -skirt 4 by vthe apertures 4, which extend up to the head portion on one sie of the lugs, but onl `a fraction of that di tance on the other si e'of thelugs. Either `two or three ribs' ma be used to support eachwrist pin lug in p ace of the single rib 3 shown, if desired, just so the. construction in any case is strong enough so that no breakage will ever be possible.

The skirt`4y `is provided on the side which 4has the high apertures 4", with the single,

slightly diagonal, longitudinal cut 5, connecting'at its upper end with the transverse The transverse cut 6 connects at its ends with the apertures 4, adjacent the wrist pin lugs 1. The wrist pin lugs 1 may be used as las bearings, bushed if desired, and the wrist pin may be. clamped in the connecting rod' instead of locked in the wrist pin lugs as shown; the essentials of the piston being the 4same in either case.

The expanding ring/7 ts in the internal ring groove in the skirt'4 below the aper- -tures 4a. The sli htly thicker portion forming the internal rlng 8 at the lower extremity of the skirt is of the cut 5 withthe lugs 1. These ribs 9 ,may be varied in shape and dimensions, and l also in. length aswell as in the points of their attachment with both the skirt and the lugs, so that it can be seen that a wide range of flexibility o f the skirt .may be obtained provided to facilitate finish-I by proper variation in the design of 'these ribs 9.

If desired, the rib- 2, joining the lugs 1 on the side opposite the cut 5 may be employed to stiifen the lugs against movement due to the connection with the skirt through the ribs 9.

The portion of the piston above the transverse cut 6 is to be given enough clearance with the cylinder wall so that it can never touch the cylinder walll under any condih well as the conditions under which it must operatef Considered in a longitudinal direction, the

ribs 9 space the skirt of the piston some disl tance from the point of rigid support, so that there is no point of the skirt supported by the ribs 9 that is contiguous to a rigid section that touches the cylinder walls.

Considered in a lcirculardirection` the relieved areas adjacent the extremities of the wrist pin bore precludes any part of the flexible portion of the skirt from being contiguous toY a rigid section thereof.

It can now be seen that this piston is much stronger than the Hatch piston, that the position of the ribs 9 make it much easier to withdraw the metal cores in the die-casting process; that practically equal flexibility over the entire surfaceof the cut side that bears against the cylinder wall is obtained; and that the amount of fiexibility may be varied as desired by proper design and dimensions.

Having now described my invention, what directlyto said head section upon but one i side of a center line, and directly to said wrist pin lugs for but a part of their adjacent sides, and provided with a4 single longitudinal cut on the other side of said center line, and with exible means on eitherl side of said cut lugs.

2./A piston composed of a head section provided with a plurality of piston ring grooves and with wrist pin lugs rigidly integralv therewith, a skirt section com osed of two faces adapted to contact wit the cylinder wall with the intermediate portions joining said skirt to said relieved, one of said faces being directly attached to said head section and to part of said wrist pin lugs, the other face being separate from said head section and said lugs and provided with a single longitudinal cut and with flexible means on either side of said cut connecting said face directly to said lu s.

A piston composed of a head section provided with wrist pin lugs rigidly integral therewith,'a skirt section depending from said head sectionl and separated from said wrist pin lugs by apertures for a part of their perlphery and provided with a solid thrust face and a flexible thrust face, the portions separating these two faces being relieved so as not to touch the cylinder Wall, the flexible thrust face being provided with a single longitudinal out and with a transverse cut in connection therewith and con- 'necting with said apertures, and flexiblemeans connecting the flexible thrust face with said lugs.

4. A piston composed of a head section with wrist pin lugs integral therewith, a skirt section depending from said head section and attached thereto at only art of its periphery, and provided opposite said part with a longitudinal c'ut and flexible lieved portions, said separated part beingv provided with a longitudinal, cut therethrough and with flexible means connecting it with said lugs. y

6. A piston composed of a head section with wrist pin lugs integral therewith, a skirt section depending from said head section and attached thereto at only part of its periphery, and provided opposite said part with a longitudinal cut, iiexible means on either side of said cut connecting said skirt to said lugs, and expanding means within said skirt section.

V7. A piston composed of a head section with wrist pin lugs integral therewith, a skirt section depending from said headsection and attached thereto at only part of its periphery, and provided oppositesaid part with a longitudinal cut, flexible means on either side of said cut connecting said skirt to said lugs, an internal ring groove within said skirt and expanding means within said groove.

c 8. A piston composed of a head section with wrist pin lugs, a skirt section composed of two'face's joined by relieved portions, one of said faces extending for less than 180 and attached direct to said head section and to a portion of said lugs, the

. other of said faces having no direct connection with said head section or Said. lugs, and i provided with a single longitudinal cut and with flexible means connecting with said lugs.

9. A iston composed of a head section with wrist pin lugs, a skirt section composed of two faces joined by relieved portions, one of said faces extending for less than 180 and attached direct to said head section and to a portion of said lugs, the other of said faces having no direct connection with said head section or said lugs, and provided with a single longitudinal cut and with lexible lmeans connecting with said lugs, and'expanding means Within said skirt section.

ROLLAND S. TROTT. I 

